Diamondback Moth, Plutella xylostella (L.), (Lepidoptera: Plutellidae ), and Other Insects of Canola, Brassica napus L., in Gauteng Province, South Africa
- Authors: Mosiane, M S
- Date: 2002
- Subjects: Plutellidae , Plutellidae -- South Africa -- Gauteng , Rape (Plant) -- South Africa -- Gauteng , Canola , Plant parasites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5937 , http://hdl.handle.net/10962/d1018250
- Description: Canola, Brassics napus L. is a relatively new crop in South Africa. Insect pests have not yet been a major problem, but the notorious brassica specialist, diamondback moth (DBM), Plutella xylostella (L.) (Plutellidae) is establishing itself as a serious pest of this crop. DBM is the most important insect pest of plants from the family Brassicaceae throughout the world. It has developed resistance to all chemical pesticides used against it in the field and to toxins of the bacterium Bacillus thuringiensis. The pest status of DBM in South Africa is lower than in other countries with similar climates. However, due to indiscriminate use of pesticides, local populations of DBM are showing signs of resistance. An initial survey has indicated that in addition to DBM, canola is also attacked by aphids, Myzus persicae (Sulzer), Brevicoryne brassicae (L.), Lipaphis e1ysimi (Kaltenbach), (Aphiade), thrips, Thrips tabaci (Lindeman) and other pests mostly brassica specialists. The study was initiated to determine the composition of the community of insects found on canola, the seasonal phenology of DBM populations in canola, and the composition, relative abundance and seasonality of its parasitoids. Monitoring of the insects was carried out at weekly intervals for three years at Rietondale and Bapsfontein in Gauteng province of South Africa. Berlese funnels have been found to be useful in extracting insects from plants, and were used to indicate the presence ofDBM larvae and other insects found on canola. Adults of DBM were monitored with synthetic pheromone traps; larval and pupal populations were monitored by scouting canola plants. Samples of larvae, pupae and parasitoid cocoons were brought into the laboratory. Parasitoids that emerged were identified and their incidence recorded. Monolepta cf bifasciata (Chrysomelidae) and Listroderes costrirostris (Schoener) (Curculionidae) were the most abundant of the coleopteran pests. (DBM) and Heliothis armigera (H.) (Noctuidae) were most abundant lepidopteran pests of Canola. There was a high proportion of first and second instar larvae as indicated by the results of the Berlese funnels as compared to visual scouting in Bapsfontein. From May to August the infestation level of DBM was high, reaching the maximum of 0.25 larvae per plant in June 1996, then declined and remained low for the rest of the season in Rietondale. From September to December for all three years of the study, the population levels Of DBM were high, reaching a maximum of 9.6larvae per plant in September 1997, and remained low from January to August in Bapsfontein. The number of adult moths per trap per week ranged from 0 to 91 in Rietondale, peaking in January 1996 and September 1997. There was no correlation between infestation levels and the pheromone trap catches. In contrast to Rietondale, there was a high correlation between pheromone trap catches and subsequent larval infestations at Bapsfontein. Although DBM infestation levels were generally low, parasitism levels often reached 100% caused by a complex of parasitoids. During the period of study, the following hymenopteran parasitoids were recorded: Cotesia plutellae (Kurdjumov) and Apanteles eriophyes (Nixon), Braconidae), both larval parasitoids, Diadegma mollipla (Holmgren) (Ichneumonidae), and Oomyzus sokolowskii (Kurdjumov) (Eulophidae), larval-pupal parasitoids, Diadromus collaris (Gravenhorst) (Ichneumonidae) pupal parasitoid, and the hyperparasitoids Mesochorus sp. (Ichneumonidae) and Pteromalus sp. (Pteromalidae). Cotesia plutellae was the most abundant parasitoid occurring throughout the year..
- Full Text:
- Date Issued: 2002
- Authors: Mosiane, M S
- Date: 2002
- Subjects: Plutellidae , Plutellidae -- South Africa -- Gauteng , Rape (Plant) -- South Africa -- Gauteng , Canola , Plant parasites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5937 , http://hdl.handle.net/10962/d1018250
- Description: Canola, Brassics napus L. is a relatively new crop in South Africa. Insect pests have not yet been a major problem, but the notorious brassica specialist, diamondback moth (DBM), Plutella xylostella (L.) (Plutellidae) is establishing itself as a serious pest of this crop. DBM is the most important insect pest of plants from the family Brassicaceae throughout the world. It has developed resistance to all chemical pesticides used against it in the field and to toxins of the bacterium Bacillus thuringiensis. The pest status of DBM in South Africa is lower than in other countries with similar climates. However, due to indiscriminate use of pesticides, local populations of DBM are showing signs of resistance. An initial survey has indicated that in addition to DBM, canola is also attacked by aphids, Myzus persicae (Sulzer), Brevicoryne brassicae (L.), Lipaphis e1ysimi (Kaltenbach), (Aphiade), thrips, Thrips tabaci (Lindeman) and other pests mostly brassica specialists. The study was initiated to determine the composition of the community of insects found on canola, the seasonal phenology of DBM populations in canola, and the composition, relative abundance and seasonality of its parasitoids. Monitoring of the insects was carried out at weekly intervals for three years at Rietondale and Bapsfontein in Gauteng province of South Africa. Berlese funnels have been found to be useful in extracting insects from plants, and were used to indicate the presence ofDBM larvae and other insects found on canola. Adults of DBM were monitored with synthetic pheromone traps; larval and pupal populations were monitored by scouting canola plants. Samples of larvae, pupae and parasitoid cocoons were brought into the laboratory. Parasitoids that emerged were identified and their incidence recorded. Monolepta cf bifasciata (Chrysomelidae) and Listroderes costrirostris (Schoener) (Curculionidae) were the most abundant of the coleopteran pests. (DBM) and Heliothis armigera (H.) (Noctuidae) were most abundant lepidopteran pests of Canola. There was a high proportion of first and second instar larvae as indicated by the results of the Berlese funnels as compared to visual scouting in Bapsfontein. From May to August the infestation level of DBM was high, reaching the maximum of 0.25 larvae per plant in June 1996, then declined and remained low for the rest of the season in Rietondale. From September to December for all three years of the study, the population levels Of DBM were high, reaching a maximum of 9.6larvae per plant in September 1997, and remained low from January to August in Bapsfontein. The number of adult moths per trap per week ranged from 0 to 91 in Rietondale, peaking in January 1996 and September 1997. There was no correlation between infestation levels and the pheromone trap catches. In contrast to Rietondale, there was a high correlation between pheromone trap catches and subsequent larval infestations at Bapsfontein. Although DBM infestation levels were generally low, parasitism levels often reached 100% caused by a complex of parasitoids. During the period of study, the following hymenopteran parasitoids were recorded: Cotesia plutellae (Kurdjumov) and Apanteles eriophyes (Nixon), Braconidae), both larval parasitoids, Diadegma mollipla (Holmgren) (Ichneumonidae), and Oomyzus sokolowskii (Kurdjumov) (Eulophidae), larval-pupal parasitoids, Diadromus collaris (Gravenhorst) (Ichneumonidae) pupal parasitoid, and the hyperparasitoids Mesochorus sp. (Ichneumonidae) and Pteromalus sp. (Pteromalidae). Cotesia plutellae was the most abundant parasitoid occurring throughout the year..
- Full Text:
- Date Issued: 2002
Distributed control applications using local area networks: a LAN based power control system at Rhodes University
- Authors: Sullivan, Anthony John
- Date: 2002
- Subjects: Embedded computer systems , Local area networks (Computer networks) , Linux
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5461 , http://hdl.handle.net/10962/d1005246 , Embedded computer systems , Local area networks (Computer networks) , Linux
- Description: This thesis describes the design and development of both the hardware and software of an embedded, distributed control system using a LAN infrastructure for communication between nodes. The primary application of this system is for power monitoring and control at Rhodes University. Both the hardware and software have been developed to provide a modular and scalable system capable of growing and adapting to meet the changing demands placed on it. The software includes a custom written Internet Protocol stack for use in the embedded environment, with a small code footprint and low processing overheads. There is also Linux-based control software, which includes a web-based device management interface and graphical output. Problems specific to the application are discussed as well as their solutions, with particular attention to the constraints of an embedded system.
- Full Text:
- Date Issued: 2002
- Authors: Sullivan, Anthony John
- Date: 2002
- Subjects: Embedded computer systems , Local area networks (Computer networks) , Linux
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5461 , http://hdl.handle.net/10962/d1005246 , Embedded computer systems , Local area networks (Computer networks) , Linux
- Description: This thesis describes the design and development of both the hardware and software of an embedded, distributed control system using a LAN infrastructure for communication between nodes. The primary application of this system is for power monitoring and control at Rhodes University. Both the hardware and software have been developed to provide a modular and scalable system capable of growing and adapting to meet the changing demands placed on it. The software includes a custom written Internet Protocol stack for use in the embedded environment, with a small code footprint and low processing overheads. There is also Linux-based control software, which includes a web-based device management interface and graphical output. Problems specific to the application are discussed as well as their solutions, with particular attention to the constraints of an embedded system.
- Full Text:
- Date Issued: 2002
Dublin founders of ringing bells
- Authors: Lewis, Colin A
- Date: 2002
- Language: English
- Type: Article
- Identifier: vital:6174 , http://hdl.handle.net/10962/d1012366 , http://www.ringingworld.co.uk
- Description: Colin Lewis was Professor of Geography at Rhodes University, Grahamstown, South Africa from 1989 until his retirement at the end of 2007. In 1990, with the strong support of the incumbent Vice-Chancellor, Dr Derek Henderson, he instigated the Certificate in Change Ringing (Church Bell Ringing) in the Rhodes University Department of Music and Musicology - the first such course to be offered in Africa. Since that date he has lectured in the basic theory, and taught the practice of change ringing. He is the Ringing Master of the Cathedral of St Michael and St George, Grahamstown, South Africa. , The refurbishment and rehanging in a new frame in 1989 of the eight bells of St Patrick's Cathedral in Melbourne, Australia, was an indirect compliment to the quality of Irish workmanship. The bells, with a tenor of 13½ cwt, were cast in Dublin by Murphy's Bell Foundry to the order of Bishop Goold. They arrived in Melbourne in 1853. The bells were intended for St Francis' Church in Elizabeth Street, Melbourne, which had no tower! Eventually, in 1868, they were hung in the south tower of the cathedral. During the nineteenth and twentieth centuries there were at least four founders in Dublin who cast ringing bells: John Murphy, James Sheridan, Thomas Hodges and Matthew O'Byrne.
- Full Text:
- Date Issued: 2002
- Authors: Lewis, Colin A
- Date: 2002
- Language: English
- Type: Article
- Identifier: vital:6174 , http://hdl.handle.net/10962/d1012366 , http://www.ringingworld.co.uk
- Description: Colin Lewis was Professor of Geography at Rhodes University, Grahamstown, South Africa from 1989 until his retirement at the end of 2007. In 1990, with the strong support of the incumbent Vice-Chancellor, Dr Derek Henderson, he instigated the Certificate in Change Ringing (Church Bell Ringing) in the Rhodes University Department of Music and Musicology - the first such course to be offered in Africa. Since that date he has lectured in the basic theory, and taught the practice of change ringing. He is the Ringing Master of the Cathedral of St Michael and St George, Grahamstown, South Africa. , The refurbishment and rehanging in a new frame in 1989 of the eight bells of St Patrick's Cathedral in Melbourne, Australia, was an indirect compliment to the quality of Irish workmanship. The bells, with a tenor of 13½ cwt, were cast in Dublin by Murphy's Bell Foundry to the order of Bishop Goold. They arrived in Melbourne in 1853. The bells were intended for St Francis' Church in Elizabeth Street, Melbourne, which had no tower! Eventually, in 1868, they were hung in the south tower of the cathedral. During the nineteenth and twentieth centuries there were at least four founders in Dublin who cast ringing bells: John Murphy, James Sheridan, Thomas Hodges and Matthew O'Byrne.
- Full Text:
- Date Issued: 2002
Dynamics of early stage fishes associated with selected warm temperate estuaries in South Africa
- Authors: Strydom, Nadine Amelia
- Date: 2002
- Subjects: Estuarine fishes -- South Africa Fishes -- Infancy -- South Africa Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5262 , http://hdl.handle.net/10962/d1005106
- Description: Early stage fishes, namely larvae and early juveniles, were collected from 12 estuaries and associated habitats in the warm temperate region of South Africa between July 1998 and December 2000. This study served to provide new information and expand on existing knowledge of early stage fish assemblages associated with various types of Eastern Cape estuaries. A total of 65 536 predominantly postflexion fish larvae were collected. Together with early juveniles, taxa comprised 72 species from 25 teleost fish families. Surf zones associated with two intermittently open estuaries showed that estuary-dependent marine species predominated in this zone. Early stage fishes responded positively during natural estuary opening events and concentrated along the estuary outflow plume, suggesting that cueing from estuary and/or river water may be taking place. A habitat study in the Swartkops Estuary, using light traps, showed that newly recruited larval fishes concentrated along the margins of the estuary and unlike their older juvenile counterparts, were poorly represented in eelgrass beds. A multi-estuary comparison, including seven permanently open and five intermittently open estuaries, indicated that early stage fish assemblages were more diverse than indicated by past investigations. Early stage fishes were also shown to concentrate in the mesohaline regions of these estuaries. Studies of estuaries with altered freshwater flow regimes were also included in the research. A regulated release of dam water in the euhaline Kromme Estuary failed to induce a cueing response from estuary-dependent marine fish larvae. This project showed that large amounts of freshwater are required to reverse the negative effects of river impoundments. The release study did show that estuary-resident fishes were sensitive to small natural pulses of freshwater and responded by spawning. However, excessive river supply through an inter-basin water transfer scheme was shown to have a flushing effect on the larvae and early juveniles of the estuary-resident Gilchristella aestuaria in the upper reaches of the Great Fish Estuary. This effect was evident in comparisons with the freshwater starved Kariega Estuary where concentrations of G. aestuaria, a species usually more abundant in freshwater rich estuaries, were considerably higher. This finding suggests that freshwater minima and maxima be considered when assessing and managing estuarine systems.
- Full Text:
- Date Issued: 2002
- Authors: Strydom, Nadine Amelia
- Date: 2002
- Subjects: Estuarine fishes -- South Africa Fishes -- Infancy -- South Africa Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5262 , http://hdl.handle.net/10962/d1005106
- Description: Early stage fishes, namely larvae and early juveniles, were collected from 12 estuaries and associated habitats in the warm temperate region of South Africa between July 1998 and December 2000. This study served to provide new information and expand on existing knowledge of early stage fish assemblages associated with various types of Eastern Cape estuaries. A total of 65 536 predominantly postflexion fish larvae were collected. Together with early juveniles, taxa comprised 72 species from 25 teleost fish families. Surf zones associated with two intermittently open estuaries showed that estuary-dependent marine species predominated in this zone. Early stage fishes responded positively during natural estuary opening events and concentrated along the estuary outflow plume, suggesting that cueing from estuary and/or river water may be taking place. A habitat study in the Swartkops Estuary, using light traps, showed that newly recruited larval fishes concentrated along the margins of the estuary and unlike their older juvenile counterparts, were poorly represented in eelgrass beds. A multi-estuary comparison, including seven permanently open and five intermittently open estuaries, indicated that early stage fish assemblages were more diverse than indicated by past investigations. Early stage fishes were also shown to concentrate in the mesohaline regions of these estuaries. Studies of estuaries with altered freshwater flow regimes were also included in the research. A regulated release of dam water in the euhaline Kromme Estuary failed to induce a cueing response from estuary-dependent marine fish larvae. This project showed that large amounts of freshwater are required to reverse the negative effects of river impoundments. The release study did show that estuary-resident fishes were sensitive to small natural pulses of freshwater and responded by spawning. However, excessive river supply through an inter-basin water transfer scheme was shown to have a flushing effect on the larvae and early juveniles of the estuary-resident Gilchristella aestuaria in the upper reaches of the Great Fish Estuary. This effect was evident in comparisons with the freshwater starved Kariega Estuary where concentrations of G. aestuaria, a species usually more abundant in freshwater rich estuaries, were considerably higher. This finding suggests that freshwater minima and maxima be considered when assessing and managing estuarine systems.
- Full Text:
- Date Issued: 2002
Economic impact of international labour migration on Lesotho's development, 1986-1998: towards an international labour migration policy for the Southern African region
- Authors: Maro, Mkasafari Grace
- Date: 2002
- Subjects: Migrant labor -- South Africa , Migrant labor -- Lesotho , Foreign workers -- South Africa , Miners -- South Africa , Miners -- Labor unions -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:1058 , http://hdl.handle.net/10962/d1007496 , Migrant labor -- South Africa , Migrant labor -- Lesotho , Foreign workers -- South Africa , Miners -- South Africa , Miners -- Labor unions -- South Africa
- Description: The aim of the thesis is to identify the pressures that contributed to the rise in international labour migration in Lesotho, and to investigate how these pressures are impacting upon the modernization process in the country, particularly at a time when employment opportunities are scarce in the southern African region. International labour migration has been used as a development tool throughout history, but especially in the 20th century by developing countries with dual labour markets. Newly independent developing countries with dual labour markets adapted the strategy of import substitution industrialization (lSI), with an emphasis on protecting infant industries and promoting pro-labour policies. In the post-colonial period the international demand for lowskilled workers rose, particularly in the North (developed countries), and in mineral rich countries including the oil exporters and South Africa, and the newly industrialising countries in East Asia. International labour migration to these countries was adapted as an integral development tool by the governments of the lSI countries. Most migrants were low-skilled and temporary workers in the destination countries. Although no multilateral institutional framework existed, usually both the sending and receiving countries adapted unilateral and bilateral migration policies to guarantee the gains from migration. Workers were thus "protected" to varying degrees under such agreements. From the 1970s, the North experienced a slowdown in the growth in demand for unskilled workers. In the 1980s, many lSI countries experienced devastating economic crises that forced them to abandon the lSI policy and adapt the export-led industrialisation (EOI) policy with an emphasis on trade liberalization. The switch from lSI to EOI in developing countries with dual labour markets led to the downsizing of public sector employment, the removal of marketing boards formally used by small-scale agricultural farmers, and the expansion of export processing zones (EPZs). These outcomes resulted in a rise in push internal migration, and international migration from these countries especially to other developing countries. At the same time, since the late 1980s, capital has acquired greatly enhanced mobility at the global level. The adaptation of EOI and the full mobility of capital at the global level altered the institutional structure within which labour migration was governed both nationally, and internationally. At the national level stricter unilateral policies were reinforced by receiving countries for low-skilled labour, while less strict policies applied for skilled labour. These remain in operation in conjunction with the earlier bilateral agreements. At the international level, there remains a lack of policy to regulate international labour migration. Under the current enhanced mobility of capital, international migrants are thus left vulnerable. Lesotho fits this pattern. Faced with a dual economy and an abundance of semi-skilled labour, Lesotho has been a principal supplier of labour to the South Africa's mining industry since its independence. Lesotho's industrial diversification thus mirrors South Africa's industrial diversification. In the lSI phase (1968 - 1987), international labour migration became the most important tool of economic welfare generation in Lesotho. Bilateral agreements were signed in the early 1970s between Lesotho and South Africa to guarantee the gains from migration. Since the late I980s, the mining industry in South Africa began to downsize production and employment. Fewer novice miners from Lesotho were recruited to work in South Africa. The adaptation of the EOI policy in Lesotho in 1987 introduced EPZ industrialization and trade liberalization. Nevertheless, the retrenchment of mine workers from South Africa is occurring at a time when Lesotho is experiencing an employment crisis. The political independence of South Africa in 1994 was accompanied by stricter international migration policies by the new democratic government of South Africa. Most migrant workers in South Africa are thus now faced with a two-door policy (of the earlier bilateral agreements and the amendments to the Aliens Control Act). This system has left migrant workers vulnerable to exploitation by both employers and the law (police) in South Africa. Nevertheless, international migration from Lesotho to South Africa continues to expand, particularly of the new type of migration - semiskilled female workers in the services sector. At the same time, South Africa is also experiencing an employment crisis. The most important policy implications are, firstly, that migration is subject to the same "casualisation" as other work, with the effects made worse by the "statelessness" of migrants, who are most vulnerable to exploitation. Secondly, multilateralism is needed (e.g., SADC) and holistic, multilateral policies are required. It is clear that under the new global division of labour ad hoc policy towards international labour migration is ineffective.
- Full Text:
- Date Issued: 2002
- Authors: Maro, Mkasafari Grace
- Date: 2002
- Subjects: Migrant labor -- South Africa , Migrant labor -- Lesotho , Foreign workers -- South Africa , Miners -- South Africa , Miners -- Labor unions -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:1058 , http://hdl.handle.net/10962/d1007496 , Migrant labor -- South Africa , Migrant labor -- Lesotho , Foreign workers -- South Africa , Miners -- South Africa , Miners -- Labor unions -- South Africa
- Description: The aim of the thesis is to identify the pressures that contributed to the rise in international labour migration in Lesotho, and to investigate how these pressures are impacting upon the modernization process in the country, particularly at a time when employment opportunities are scarce in the southern African region. International labour migration has been used as a development tool throughout history, but especially in the 20th century by developing countries with dual labour markets. Newly independent developing countries with dual labour markets adapted the strategy of import substitution industrialization (lSI), with an emphasis on protecting infant industries and promoting pro-labour policies. In the post-colonial period the international demand for lowskilled workers rose, particularly in the North (developed countries), and in mineral rich countries including the oil exporters and South Africa, and the newly industrialising countries in East Asia. International labour migration to these countries was adapted as an integral development tool by the governments of the lSI countries. Most migrants were low-skilled and temporary workers in the destination countries. Although no multilateral institutional framework existed, usually both the sending and receiving countries adapted unilateral and bilateral migration policies to guarantee the gains from migration. Workers were thus "protected" to varying degrees under such agreements. From the 1970s, the North experienced a slowdown in the growth in demand for unskilled workers. In the 1980s, many lSI countries experienced devastating economic crises that forced them to abandon the lSI policy and adapt the export-led industrialisation (EOI) policy with an emphasis on trade liberalization. The switch from lSI to EOI in developing countries with dual labour markets led to the downsizing of public sector employment, the removal of marketing boards formally used by small-scale agricultural farmers, and the expansion of export processing zones (EPZs). These outcomes resulted in a rise in push internal migration, and international migration from these countries especially to other developing countries. At the same time, since the late 1980s, capital has acquired greatly enhanced mobility at the global level. The adaptation of EOI and the full mobility of capital at the global level altered the institutional structure within which labour migration was governed both nationally, and internationally. At the national level stricter unilateral policies were reinforced by receiving countries for low-skilled labour, while less strict policies applied for skilled labour. These remain in operation in conjunction with the earlier bilateral agreements. At the international level, there remains a lack of policy to regulate international labour migration. Under the current enhanced mobility of capital, international migrants are thus left vulnerable. Lesotho fits this pattern. Faced with a dual economy and an abundance of semi-skilled labour, Lesotho has been a principal supplier of labour to the South Africa's mining industry since its independence. Lesotho's industrial diversification thus mirrors South Africa's industrial diversification. In the lSI phase (1968 - 1987), international labour migration became the most important tool of economic welfare generation in Lesotho. Bilateral agreements were signed in the early 1970s between Lesotho and South Africa to guarantee the gains from migration. Since the late I980s, the mining industry in South Africa began to downsize production and employment. Fewer novice miners from Lesotho were recruited to work in South Africa. The adaptation of the EOI policy in Lesotho in 1987 introduced EPZ industrialization and trade liberalization. Nevertheless, the retrenchment of mine workers from South Africa is occurring at a time when Lesotho is experiencing an employment crisis. The political independence of South Africa in 1994 was accompanied by stricter international migration policies by the new democratic government of South Africa. Most migrant workers in South Africa are thus now faced with a two-door policy (of the earlier bilateral agreements and the amendments to the Aliens Control Act). This system has left migrant workers vulnerable to exploitation by both employers and the law (police) in South Africa. Nevertheless, international migration from Lesotho to South Africa continues to expand, particularly of the new type of migration - semiskilled female workers in the services sector. At the same time, South Africa is also experiencing an employment crisis. The most important policy implications are, firstly, that migration is subject to the same "casualisation" as other work, with the effects made worse by the "statelessness" of migrants, who are most vulnerable to exploitation. Secondly, multilateralism is needed (e.g., SADC) and holistic, multilateral policies are required. It is clear that under the new global division of labour ad hoc policy towards international labour migration is ineffective.
- Full Text:
- Date Issued: 2002
Economic security and the social science literature on teenage pregnancy in South Africa
- Authors: Macleod, Catriona I
- Date: 2002
- Language: English
- Type: Article
- Identifier: vital:6253 , http://hdl.handle.net/10962/d1007871
- Description: Feminists have argued that the association made between teenage childbearing and long-term lower socioeconomic status hides a multitude of socially constructed inequalities. I extend this position by analysing how the association is linked in the South African literature on teenage pregnancy to economic security. I utilise Foucault’s conceptualization of the method of security. Security refers to institutions and practices that defend and maintain a national population as well as secure the economic, demographic, and social processes of that population. I analyse how the traits of the method of security are deployed with regard to teenage pregnancy; how reproductive adolescents are viewed as disrupting the production of the economic self and fracturing population control, thereby threatening economic security; and how the invocation of economic security allows for the legitimation of various regulatory practices. , Rhodes University
- Full Text:
- Date Issued: 2002
- Authors: Macleod, Catriona I
- Date: 2002
- Language: English
- Type: Article
- Identifier: vital:6253 , http://hdl.handle.net/10962/d1007871
- Description: Feminists have argued that the association made between teenage childbearing and long-term lower socioeconomic status hides a multitude of socially constructed inequalities. I extend this position by analysing how the association is linked in the South African literature on teenage pregnancy to economic security. I utilise Foucault’s conceptualization of the method of security. Security refers to institutions and practices that defend and maintain a national population as well as secure the economic, demographic, and social processes of that population. I analyse how the traits of the method of security are deployed with regard to teenage pregnancy; how reproductive adolescents are viewed as disrupting the production of the economic self and fracturing population control, thereby threatening economic security; and how the invocation of economic security allows for the legitimation of various regulatory practices. , Rhodes University
- Full Text:
- Date Issued: 2002
Effect of selected physical and production traits on the tick burdens of beef cattle
- Authors: Botha, Theunis Christoffel
- Date: 2002
- Subjects: Beef cattle -- Breeding
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10966 , http://hdl.handle.net/10948/91 , Beef cattle -- Breeding
- Description: The objective of this study was to determine the effect of selected traits such as age, sex, body weight, body length and height, body condition score (BCS), coatscore (CS), skin thickness and average skin surface temperature on tick burdens in beef cattle. Bonsmara cattle (n= 143) were used to measure visible tick counts, body condition score, coat score, skin thickness, body height and length, body weight, body surface temperature, gender and inter calving period. Measurements were taken from April to December. All animals were managed extensively on natural and cultivated pastures near George in the Southern Cape. Female animals had significantly (p<0.05) greater tick infestation (37.98±2.7) compared to male animals (16.52±1.2). Age was a significant factor (p<0.001) with the younger animals below two years having (46.40±5.26) more ticks than those of two years and older (20.15±2.44). A significant negative correlation (p<0.001; -0.29) was reported between the infestation of ticks on the animals and the age of the animal. Animals with an average body weight below 250kg had 42% (p<0.05) more ticks compared to animals with a body weight above 250kg. Age of the animal and weight were highly correlated (r= 0.70); p<0.001), while the correlation between the number of ticks per cow and the mean weight was negatively correlated (r= -0.37; p<0.001). Skin surface temperature significantly influenced tick infestation on the animals (p<0.001). The degree of infestation increased as body surface temperature exceeded 30º C. Coat score, skin thickness, body condition score and inter calving period did not significantly influence tick infestation on the animals. The infestation of ticks on the animals were significantly influenced by body height (p<0.019) and body length (p<0.001). Animals smaller than a 130cm in height had a significantly (p<0.05) greater tick infestation (36.5±5) compared to animals taller than 130cm (21.2±1.5). This trend was also observed for body length. Animals with a body length shorter than 145cm had a greater (p<0.05) average tick infestation of 41.3±4.5 compared to 23.2±1.3 to animals longer than 145cm, indicating a 44% greater tick infestation in favour of the shorter animals. For increased production and tick resistance animals should have smoother coats and be able to dissipate heat effectively.
- Full Text:
- Date Issued: 2002
- Authors: Botha, Theunis Christoffel
- Date: 2002
- Subjects: Beef cattle -- Breeding
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10966 , http://hdl.handle.net/10948/91 , Beef cattle -- Breeding
- Description: The objective of this study was to determine the effect of selected traits such as age, sex, body weight, body length and height, body condition score (BCS), coatscore (CS), skin thickness and average skin surface temperature on tick burdens in beef cattle. Bonsmara cattle (n= 143) were used to measure visible tick counts, body condition score, coat score, skin thickness, body height and length, body weight, body surface temperature, gender and inter calving period. Measurements were taken from April to December. All animals were managed extensively on natural and cultivated pastures near George in the Southern Cape. Female animals had significantly (p<0.05) greater tick infestation (37.98±2.7) compared to male animals (16.52±1.2). Age was a significant factor (p<0.001) with the younger animals below two years having (46.40±5.26) more ticks than those of two years and older (20.15±2.44). A significant negative correlation (p<0.001; -0.29) was reported between the infestation of ticks on the animals and the age of the animal. Animals with an average body weight below 250kg had 42% (p<0.05) more ticks compared to animals with a body weight above 250kg. Age of the animal and weight were highly correlated (r= 0.70); p<0.001), while the correlation between the number of ticks per cow and the mean weight was negatively correlated (r= -0.37; p<0.001). Skin surface temperature significantly influenced tick infestation on the animals (p<0.001). The degree of infestation increased as body surface temperature exceeded 30º C. Coat score, skin thickness, body condition score and inter calving period did not significantly influence tick infestation on the animals. The infestation of ticks on the animals were significantly influenced by body height (p<0.019) and body length (p<0.001). Animals smaller than a 130cm in height had a significantly (p<0.05) greater tick infestation (36.5±5) compared to animals taller than 130cm (21.2±1.5). This trend was also observed for body length. Animals with a body length shorter than 145cm had a greater (p<0.05) average tick infestation of 41.3±4.5 compared to 23.2±1.3 to animals longer than 145cm, indicating a 44% greater tick infestation in favour of the shorter animals. For increased production and tick resistance animals should have smoother coats and be able to dissipate heat effectively.
- Full Text:
- Date Issued: 2002
Effects of axial ligands on the photophysical properties of silicon octaphenoxyphthalocyanine
- Maree, M David, Nyokong, Tebello, Suhling, Klaus, Phillips, David
- Authors: Maree, M David , Nyokong, Tebello , Suhling, Klaus , Phillips, David
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289582 , vital:56651 , xlink:href="https://doi.org/10.1142/S1088424602000452"
- Description: The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.
- Full Text:
- Date Issued: 2002
- Authors: Maree, M David , Nyokong, Tebello , Suhling, Klaus , Phillips, David
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/289582 , vital:56651 , xlink:href="https://doi.org/10.1142/S1088424602000452"
- Description: The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.
- Full Text:
- Date Issued: 2002
Effects of Axial Ligands on the Photosensitising Properties of Silicon Octaphenoxyphthalocyanines
- Authors: Maree, Machiel David
- Date: 2002
- Subjects: Ligands , Photochemotherapy , Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4553 , http://hdl.handle.net/10962/d1018246
- Description: Various axially substituted Silicon octaphenoxyphthalocyanines were synthesised as potential photosensitisers in the photodynamic therapy of cancer. Conventional reflux reactions were used for synthesis as well as new microwave irradiation reactions, wherein the reaction times were decreased tenfold with a marginal increase in reaction yield and product purity. An interesting series of oligomeric (dimer to a nonamer) silicon octaphenoxyphthalocyanines were also successfully synthesised in a reaction similar to polymerisation reactions. These compounds were found to undergo an axial ligand transformation upon irradiation with red light (> 600 nm) in dimethylsulphoxide solution. All the ligands were transformed into the dihydroxy silicon octaphenoxyphthalocyanine with varying degrees of phototransformation quantum yields ranging in order from 10⁻³ to 10⁻⁵ depending on the axial ligand involved. During and after axial ligand transformations a photodegredation of the dihydroxy silicon octaphenoxy phthalocyanine was observed upon continued irradiation. The oligomers were found to undergo the same axial ligand transformation process with a phototransformation quantum yield of 10⁻⁵ The singlet oxygen quantum yields of the unaggregated monomeric silicon octaphenoxy phthalocyanines were all found to be approximately 0.2 with the exception of a compound with two (trihexyl)siloxy axial substituents that had a singlet oxygen quantum yield of approximately 0.4 in dimethylsulphoxide solutions. The oligomers showed a surprising trend of an increase in singlet oxygen quantum yield with an increase in phthalocyanine ring number up to the pentamer and then a dramatic decrease to the nonamer. The triplet quantum yield and triplet lifetime were determined by laser flash photolysis for selected compounds and no correlation was observed with any of these properties and the singlet oxygen quantum yields. These selected compounds all fluoresce and a very good correlation was found between the fluorescence lifetimes determined experimentally by laser photolysis and the Strickler-Berg equation for the non-aggregated compounds. Electrochemical measurements also indicate the importance of the axial ligands upon the behaviour of the phthalocyanines as cyclic voltammetric behaviour was determined by the nature of the axial ligand.
- Full Text:
- Date Issued: 2002
- Authors: Maree, Machiel David
- Date: 2002
- Subjects: Ligands , Photochemotherapy , Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4553 , http://hdl.handle.net/10962/d1018246
- Description: Various axially substituted Silicon octaphenoxyphthalocyanines were synthesised as potential photosensitisers in the photodynamic therapy of cancer. Conventional reflux reactions were used for synthesis as well as new microwave irradiation reactions, wherein the reaction times were decreased tenfold with a marginal increase in reaction yield and product purity. An interesting series of oligomeric (dimer to a nonamer) silicon octaphenoxyphthalocyanines were also successfully synthesised in a reaction similar to polymerisation reactions. These compounds were found to undergo an axial ligand transformation upon irradiation with red light (> 600 nm) in dimethylsulphoxide solution. All the ligands were transformed into the dihydroxy silicon octaphenoxyphthalocyanine with varying degrees of phototransformation quantum yields ranging in order from 10⁻³ to 10⁻⁵ depending on the axial ligand involved. During and after axial ligand transformations a photodegredation of the dihydroxy silicon octaphenoxy phthalocyanine was observed upon continued irradiation. The oligomers were found to undergo the same axial ligand transformation process with a phototransformation quantum yield of 10⁻⁵ The singlet oxygen quantum yields of the unaggregated monomeric silicon octaphenoxy phthalocyanines were all found to be approximately 0.2 with the exception of a compound with two (trihexyl)siloxy axial substituents that had a singlet oxygen quantum yield of approximately 0.4 in dimethylsulphoxide solutions. The oligomers showed a surprising trend of an increase in singlet oxygen quantum yield with an increase in phthalocyanine ring number up to the pentamer and then a dramatic decrease to the nonamer. The triplet quantum yield and triplet lifetime were determined by laser flash photolysis for selected compounds and no correlation was observed with any of these properties and the singlet oxygen quantum yields. These selected compounds all fluoresce and a very good correlation was found between the fluorescence lifetimes determined experimentally by laser photolysis and the Strickler-Berg equation for the non-aggregated compounds. Electrochemical measurements also indicate the importance of the axial ligands upon the behaviour of the phthalocyanines as cyclic voltammetric behaviour was determined by the nature of the axial ligand.
- Full Text:
- Date Issued: 2002
Effects of substituents on the photosensitizing and electrocatalytic properties of phthalocyanines
- Authors: Maree, Suzanne Elizabeth
- Date: 2002
- Subjects: Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4554 , http://hdl.handle.net/10962/d1018247
- Description: In this work a selection of octasubstituted phthalocyaninato Zinc, Ge(IV) and Sn(IV) complexes were synthesized for possible use in photodynamic therapy and their photochemistry, photophysics and electrochemistry studied. Third-generation complexes containing steroids, e.g. cholesterol and estrone, were synthesized to improve tumour selectivity. The zinc phthalocyanine complexes (ZnPc) showed that complexes containing electron-donating groups have higher photostability. Germanium phthalocyanine complexes (GePc) undergo phototransformation rather than direct photobleaching and the tin phthalocyanine complexes (SnPc) undergo photobleaching mediated by photoreduction of the phthalocyanine ring. Singlet oxygen production showed increased in the following order: GePc>SnPc>ZnPc. Triplet lifetimes of the GePc (168-340μs) are very similar to that of the ZnPc (197 - 366μs), but the triplet lifetimes of the SnPc are ten fold shorter (10 - 32μs ). Triplet quantum yields are higher for the GePc (0.20 - 0.50) and SnPc (0.08 - 0.45) than for the ZnPc (0.02 - 0.25). Fluorescence lifetimes of GePc ( 4.0 - 5.1 ns) are significantly longer than that of ZnPc (1.9 - 3.0 ns) and SnPc (0.2 - 0.4 ns). Fluorescence quantum yields decrease in the following order: GePc(0.21-0.31)>ZnPc(0.02-0.21)>SnPc(0.02- 0.06). Ring-substituted cobalt phthalocyanine complexes of the form CoPc(R)4 (R= NH2, N02, C(CH3)3, S03H and COOH) are compared for their catalytic activities towards the oxidation of cysteine. The potential for the electrocatalytic oxidation of cysteine is closely related to the Com/Co11 couple of the CoPc(R)4 complexes in acidic media and to the Con/Co1 couple in basic media. The catalytic current and the oxidation potential for cysteine are dependent on the pH of the solution, the potential becoming less positive and the currents increasing with increase in pH.
- Full Text:
- Date Issued: 2002
- Authors: Maree, Suzanne Elizabeth
- Date: 2002
- Subjects: Phthalocyanines
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4554 , http://hdl.handle.net/10962/d1018247
- Description: In this work a selection of octasubstituted phthalocyaninato Zinc, Ge(IV) and Sn(IV) complexes were synthesized for possible use in photodynamic therapy and their photochemistry, photophysics and electrochemistry studied. Third-generation complexes containing steroids, e.g. cholesterol and estrone, were synthesized to improve tumour selectivity. The zinc phthalocyanine complexes (ZnPc) showed that complexes containing electron-donating groups have higher photostability. Germanium phthalocyanine complexes (GePc) undergo phototransformation rather than direct photobleaching and the tin phthalocyanine complexes (SnPc) undergo photobleaching mediated by photoreduction of the phthalocyanine ring. Singlet oxygen production showed increased in the following order: GePc>SnPc>ZnPc. Triplet lifetimes of the GePc (168-340μs) are very similar to that of the ZnPc (197 - 366μs), but the triplet lifetimes of the SnPc are ten fold shorter (10 - 32μs ). Triplet quantum yields are higher for the GePc (0.20 - 0.50) and SnPc (0.08 - 0.45) than for the ZnPc (0.02 - 0.25). Fluorescence lifetimes of GePc ( 4.0 - 5.1 ns) are significantly longer than that of ZnPc (1.9 - 3.0 ns) and SnPc (0.2 - 0.4 ns). Fluorescence quantum yields decrease in the following order: GePc(0.21-0.31)>ZnPc(0.02-0.21)>SnPc(0.02- 0.06). Ring-substituted cobalt phthalocyanine complexes of the form CoPc(R)4 (R= NH2, N02, C(CH3)3, S03H and COOH) are compared for their catalytic activities towards the oxidation of cysteine. The potential for the electrocatalytic oxidation of cysteine is closely related to the Com/Co11 couple of the CoPc(R)4 complexes in acidic media and to the Con/Co1 couple in basic media. The catalytic current and the oxidation potential for cysteine are dependent on the pH of the solution, the potential becoming less positive and the currents increasing with increase in pH.
- Full Text:
- Date Issued: 2002
Elucidation and manipulation of the Hydantoin-Hydrolysing Enzyme System of Agrobacterium tumefaciens RU-OR for the Biocatalytic production of D-amino acids
- Authors: Hartley, Carol Janet
- Date: 2002
- Subjects: Amino acids Agrobacterium tumefaciens
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3916 , http://hdl.handle.net/10962/d1003975
- Description: There is widespread interest in the biocatalytic production of enantiomerically pure D-amino acids for use in the synthesis of antibiotics, insecticides, herbicides, drug carriers and many other pharmaceuticals. Hydantoin-hydrolysing enzyme systems can be successfully utilised to stereoselectively convert racemic hydantoins into enantiomerically pure amino acid products. In fact, the use of microbial D-hydantoinase and D-stereoselective N-carbamoyl amino acid amidohydrolase activity to produce D-p-hydroxyphenylglycine from D,L-5-phydroxyphenylhydantoin has been described as one of the most successful biotechnological applications of enzyme technology developed to date. A need to utilise the novel biodiversity of South African microorganisms for the development of an indigenous process to produce enantiomerically pure amino acids was identified in 1995. Subsequently, the Rhodes Hydantoinase Group was established and several local hydantoin-hydrolysing microorganisms were isolated. The research in this study describes the isolation and selection of Agrobacterium tumefaciens RU-OR, which produced D-stereoselective hydantoinhydrolysing activity. Characterisation of the hydantoin-hydrolysing enzyme system of RU-OR revealed novel biocatalytic properties, and potential for the application of this strain for the biocatalytic production of D-amino acids. A fundamental understanding of the regulation of hydantoin-hydrolysing enzyme activity in A. tumefaciens RU-OR was established, and utilised to produce mutant strains with altered regulation of hydantoin-hydrolysing activity. These strains were used to further elucidate the mechanisms regulating the production of hydantoins-hydrolysing activity in A. tumefaciens RU-OR cells. Overproduction of hydantoinase and N-carbamoyl-D-amino acid amidohydrolase activity in selected mutant strains resulted in efficient conversion of D,L-5-p-hydroxyphenylhydantoin to D-p-hydroxyphenylglycine. Thus the establishment of a primary understanding of the hydantoin-hydrolysing enzyme system in A. tumefaciens RU-OR could be used to manipulate the hydantoin-hydrolysing activity in RU-OR cells to produce an improved biocatalyst. The isolation of A. tumfecaiens RU-OR genes encoding for hydantoin-hydrolysing activity revealed two separate N-carbamoyl-D-amino acid amidohydrolaseencoding genes (ncaR1 and ncaR2) in this bacterium with distinct chromosomal locations, nucleotide coding sequence and predicted primary amino acid sequence. The novel biocatalytic properties of the hydantoin-hydrolysing enzyme system in A. tumefaciens RU-OR and mutant derivatives present fascinating opportunities for further elucidation of the natural function, regulation and biocatalytic potential of hydantoin-hydrolysing enzymes.
- Full Text:
- Date Issued: 2002
- Authors: Hartley, Carol Janet
- Date: 2002
- Subjects: Amino acids Agrobacterium tumefaciens
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3916 , http://hdl.handle.net/10962/d1003975
- Description: There is widespread interest in the biocatalytic production of enantiomerically pure D-amino acids for use in the synthesis of antibiotics, insecticides, herbicides, drug carriers and many other pharmaceuticals. Hydantoin-hydrolysing enzyme systems can be successfully utilised to stereoselectively convert racemic hydantoins into enantiomerically pure amino acid products. In fact, the use of microbial D-hydantoinase and D-stereoselective N-carbamoyl amino acid amidohydrolase activity to produce D-p-hydroxyphenylglycine from D,L-5-phydroxyphenylhydantoin has been described as one of the most successful biotechnological applications of enzyme technology developed to date. A need to utilise the novel biodiversity of South African microorganisms for the development of an indigenous process to produce enantiomerically pure amino acids was identified in 1995. Subsequently, the Rhodes Hydantoinase Group was established and several local hydantoin-hydrolysing microorganisms were isolated. The research in this study describes the isolation and selection of Agrobacterium tumefaciens RU-OR, which produced D-stereoselective hydantoinhydrolysing activity. Characterisation of the hydantoin-hydrolysing enzyme system of RU-OR revealed novel biocatalytic properties, and potential for the application of this strain for the biocatalytic production of D-amino acids. A fundamental understanding of the regulation of hydantoin-hydrolysing enzyme activity in A. tumefaciens RU-OR was established, and utilised to produce mutant strains with altered regulation of hydantoin-hydrolysing activity. These strains were used to further elucidate the mechanisms regulating the production of hydantoins-hydrolysing activity in A. tumefaciens RU-OR cells. Overproduction of hydantoinase and N-carbamoyl-D-amino acid amidohydrolase activity in selected mutant strains resulted in efficient conversion of D,L-5-p-hydroxyphenylhydantoin to D-p-hydroxyphenylglycine. Thus the establishment of a primary understanding of the hydantoin-hydrolysing enzyme system in A. tumefaciens RU-OR could be used to manipulate the hydantoin-hydrolysing activity in RU-OR cells to produce an improved biocatalyst. The isolation of A. tumfecaiens RU-OR genes encoding for hydantoin-hydrolysing activity revealed two separate N-carbamoyl-D-amino acid amidohydrolaseencoding genes (ncaR1 and ncaR2) in this bacterium with distinct chromosomal locations, nucleotide coding sequence and predicted primary amino acid sequence. The novel biocatalytic properties of the hydantoin-hydrolysing enzyme system in A. tumefaciens RU-OR and mutant derivatives present fascinating opportunities for further elucidation of the natural function, regulation and biocatalytic potential of hydantoin-hydrolysing enzymes.
- Full Text:
- Date Issued: 2002
Employee ownership in the context of globalisation: a developing country perspective
- NALEDI
- Authors: NALEDI
- Date: 2002
- Subjects: NALEDI
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/153882 , vital:39532
- Description: This paper represents an initial set of ideas focused on employee ownership within the developing country context. The central question being explored is ‘To what extent can employee ownership support the broader goal of poverty reduction in South Africa (and, by extension, in the developing country context)?’. This is a rather broad question, and as such this note sets out to begin the discussion on this question, rather than seek to provide a definite set of answers. The critical perspectives put forward in this note draw heavily on experiences and debates in South Africa, and particularly those within the labour movement.
- Full Text:
- Date Issued: 2002
- Authors: NALEDI
- Date: 2002
- Subjects: NALEDI
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/153882 , vital:39532
- Description: This paper represents an initial set of ideas focused on employee ownership within the developing country context. The central question being explored is ‘To what extent can employee ownership support the broader goal of poverty reduction in South Africa (and, by extension, in the developing country context)?’. This is a rather broad question, and as such this note sets out to begin the discussion on this question, rather than seek to provide a definite set of answers. The critical perspectives put forward in this note draw heavily on experiences and debates in South Africa, and particularly those within the labour movement.
- Full Text:
- Date Issued: 2002
English in the prison services: a case of breaking the law?
- De Klerk, Vivian A, Barkhuizen, Gary P
- Authors: De Klerk, Vivian A , Barkhuizen, Gary P
- Date: 2002
- Language: English
- Type: Article
- Identifier: vital:6133 , http://hdl.handle.net/10962/d1011585
- Description: In this paper we report on an investigation into the use of English in a prison in the Eastern Cape Province, run by the Department of Correctional Services (CS) five years after the declaration of an official multilingual policy. The investigation consisted of a range of interviews and observations in this institution, aimed at establishing the extent to which the national language policy is actually being implemented on the ground. Findings suggest that the use of English predominates in the high, official domains, that there is a marked avoidance of Afrikaans, and that Xhosa, the main language of the Eastern Cape Province, increasingly occupies the lower, unofficial domains. Tensions between policy and practice are discussed, and it is argued that the CS has shown that pragmatism is a much stronger force than ideology. While the roles of Xhosa and Afrikaans appear to be in the process of reversing in the Grahamstown prison, English has emerged as stronger there than it has ever been before. And because it will continue to be a necessary prerequisite for the mobility and promotion of staff in the country as a whole, and the lingua franca for an increasingly mobile criminal population (which means the prisons are likely to become increasingly linguistically diverse, rather than settling into regional patterns), everyone will have to have some proficiency in English, which, ironically, will promote and strengthen it even more.
- Full Text:
- Date Issued: 2002
- Authors: De Klerk, Vivian A , Barkhuizen, Gary P
- Date: 2002
- Language: English
- Type: Article
- Identifier: vital:6133 , http://hdl.handle.net/10962/d1011585
- Description: In this paper we report on an investigation into the use of English in a prison in the Eastern Cape Province, run by the Department of Correctional Services (CS) five years after the declaration of an official multilingual policy. The investigation consisted of a range of interviews and observations in this institution, aimed at establishing the extent to which the national language policy is actually being implemented on the ground. Findings suggest that the use of English predominates in the high, official domains, that there is a marked avoidance of Afrikaans, and that Xhosa, the main language of the Eastern Cape Province, increasingly occupies the lower, unofficial domains. Tensions between policy and practice are discussed, and it is argued that the CS has shown that pragmatism is a much stronger force than ideology. While the roles of Xhosa and Afrikaans appear to be in the process of reversing in the Grahamstown prison, English has emerged as stronger there than it has ever been before. And because it will continue to be a necessary prerequisite for the mobility and promotion of staff in the country as a whole, and the lingua franca for an increasingly mobile criminal population (which means the prisons are likely to become increasingly linguistically diverse, rather than settling into regional patterns), everyone will have to have some proficiency in English, which, ironically, will promote and strengthen it even more.
- Full Text:
- Date Issued: 2002
Evaluation of broiler performance under small-scale and semi-commercial farming conditions in the Northern Province
- Authors: Nembilwi, Daniel
- Date: 2002
- Subjects: Broilers (Chickens)
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10964 , http://hdl.handle.net/10948/92 , Broilers (Chickens)
- Description: Introduction: In the Northern region of the Northern Province, there is an increase in the number of small-scale and semi-commercial farms in all sectors of agriculture. This includes the production of grains, vegetables, fruits and livestock. Broiler production seemed to be a much-preferred alternative of development in community based projects and emerging farmers have shown keen interest. This is because broiler production requires less space than ruminants and is ready for human consumption within a very short period of time. Poultry production provides a constant source of income and protein with a big customer demand. By the year 2000, broiler production is expected to reach 4000 million and 7.5 million tons of poultry feeds in the world. Many countries have initiated programs aimed at improving small-scale poultry as a means of helping to bring socio- economic benefits to rural communities (Panda, 1989). In order to feed the ever rising population of 4.9 million in the Northern Province (1996 Census), there must be an increase in the production of broilers as a primary source of top quality animal protein. With the high unemployment rate (46%) in the Northern Province, self- employment projects are needed which comply with agro- processing. More than 90 community projects based on poultry production in the Northern region of the Northern Province had been established in order to reduce the high rate of unemployment. Today more people have engaged themselves in community projects especially in poultry production than ever before. Some of the constrains of broiler production at both small-scale and semi-commercial farming condition includes inadequate ventilation system. Lack of suitable health care facilities and frequently the absence of efficient marketing structures form part of the obstacles to the rapid development of poultry production. Feed costs which remain the highest input cost in the production of broilers represent between 60 to 70% or more of the total costs of broiler productions (Benyi and Habi, 1998). Lack of management skills and training for small and semi-commercial farmers makes it difficult to obtain optimum performance. The objective of this study is to evaluate the performance of broilers as influenced by environmental factors under small.
- Full Text:
- Date Issued: 2002
- Authors: Nembilwi, Daniel
- Date: 2002
- Subjects: Broilers (Chickens)
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10964 , http://hdl.handle.net/10948/92 , Broilers (Chickens)
- Description: Introduction: In the Northern region of the Northern Province, there is an increase in the number of small-scale and semi-commercial farms in all sectors of agriculture. This includes the production of grains, vegetables, fruits and livestock. Broiler production seemed to be a much-preferred alternative of development in community based projects and emerging farmers have shown keen interest. This is because broiler production requires less space than ruminants and is ready for human consumption within a very short period of time. Poultry production provides a constant source of income and protein with a big customer demand. By the year 2000, broiler production is expected to reach 4000 million and 7.5 million tons of poultry feeds in the world. Many countries have initiated programs aimed at improving small-scale poultry as a means of helping to bring socio- economic benefits to rural communities (Panda, 1989). In order to feed the ever rising population of 4.9 million in the Northern Province (1996 Census), there must be an increase in the production of broilers as a primary source of top quality animal protein. With the high unemployment rate (46%) in the Northern Province, self- employment projects are needed which comply with agro- processing. More than 90 community projects based on poultry production in the Northern region of the Northern Province had been established in order to reduce the high rate of unemployment. Today more people have engaged themselves in community projects especially in poultry production than ever before. Some of the constrains of broiler production at both small-scale and semi-commercial farming condition includes inadequate ventilation system. Lack of suitable health care facilities and frequently the absence of efficient marketing structures form part of the obstacles to the rapid development of poultry production. Feed costs which remain the highest input cost in the production of broilers represent between 60 to 70% or more of the total costs of broiler productions (Benyi and Habi, 1998). Lack of management skills and training for small and semi-commercial farmers makes it difficult to obtain optimum performance. The objective of this study is to evaluate the performance of broilers as influenced by environmental factors under small.
- Full Text:
- Date Issued: 2002
Evaluation of manufacturing processes for the production of atrazine
- Authors: Schaefer, Melissa Claire
- Date: 2002
- Subjects: Atrazine , Pesticides
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10960 , http://hdl.handle.net/10948/96 , Atrazine , Pesticides
- Description: This report describes the results of investigations carried out with the view to find an alternative for MIBK as solvent for the production of atrazine as currently practised by Dow AgroSciences in South Africa. The main motivating factors for the said investigation was: · to increase the yield of atrazine produced, · to reduce the amount of organics, consisting essentially of reaction solvent containing dissolved product, in the aqueous process effluent, and · to improve the properties of the solid (crystalline) product to enable easier product formulation. Synthetic reactions carried out in the absence of organic solvent, i.e. in essentially a 10% NaCl solution containing a surfactant, proved rather disappointing. Low yields of atrazine were obtained together with relatively large amounts of by-products such as propazine and simazine, irrespective of the nature of the surfactant. The reason for the low yield of atrazine and high yields of by-products were established in competing substitution reactions. In these reactions, IPA was reacted with an equimolar mixture of cyanuric chloride and mono-i (first reaction intermediate) in both aqueous medium and in toluene as reaction solvent. The results of these experiments indicated that in aqueous medium IPA reacts faster with mono-i than cyanuric chloride to give propazine as by-product. In toluene, however, the preferred reaction is with cyanuric chloride to give more mono-i as product. Toluene was investigated as an alternative organic solvent to MIBK in view of its desirable properties such as low solubility in water and ease of recovery and recycling. The synthesis of atrazine was optimised in terms of addition sequence and rates of amine reagents and base (HCl acceptor), both by means of benchscale reactions and reaction calorimetry. Reaction energy profiles indicated that both the reaction of secondary amine/NaOH and primary amine/NaOH were virtually instantaneous. This implies that the reaction can be performed under feed control conditions. Of particular importance in ensuring high yields of high purity product was accurate temperature control (since both reaction steps are highly exothermic) and mixing. The latter was important in view of the rapid reaction of amine/NaOH with cyanuric chloride, as well as the possible reaction of mono-i, the first reaction intermediate, with IPA in cases of local excesses of reagent. Under optimum conditions, a yield of atrazine > 97% could be achieved where the resultant product was well within stipulated product specifications. In view of the results obtained, the following recommendations regarding the synthesis of atrazine in toluene as reaction solvent can be made: · Use a reagent addition sequence that staggers the addition of amine and NaOH in such a manner that amine is added first for a short while, followed by the simultaneous addition of amine and NaOH, and ending with NaOH. Use two reaction vessels in series, one for the IPA addition reaction and one for the MEA addition reaction. In this manner the reaction can be run on a continuous basis since no lag time between amine additions is required. Also, smaller reactors may be used whilst maintaining high production rates. Smaller reactors will improve both temperature control and mixing of reagents.
- Full Text:
- Date Issued: 2002
- Authors: Schaefer, Melissa Claire
- Date: 2002
- Subjects: Atrazine , Pesticides
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10960 , http://hdl.handle.net/10948/96 , Atrazine , Pesticides
- Description: This report describes the results of investigations carried out with the view to find an alternative for MIBK as solvent for the production of atrazine as currently practised by Dow AgroSciences in South Africa. The main motivating factors for the said investigation was: · to increase the yield of atrazine produced, · to reduce the amount of organics, consisting essentially of reaction solvent containing dissolved product, in the aqueous process effluent, and · to improve the properties of the solid (crystalline) product to enable easier product formulation. Synthetic reactions carried out in the absence of organic solvent, i.e. in essentially a 10% NaCl solution containing a surfactant, proved rather disappointing. Low yields of atrazine were obtained together with relatively large amounts of by-products such as propazine and simazine, irrespective of the nature of the surfactant. The reason for the low yield of atrazine and high yields of by-products were established in competing substitution reactions. In these reactions, IPA was reacted with an equimolar mixture of cyanuric chloride and mono-i (first reaction intermediate) in both aqueous medium and in toluene as reaction solvent. The results of these experiments indicated that in aqueous medium IPA reacts faster with mono-i than cyanuric chloride to give propazine as by-product. In toluene, however, the preferred reaction is with cyanuric chloride to give more mono-i as product. Toluene was investigated as an alternative organic solvent to MIBK in view of its desirable properties such as low solubility in water and ease of recovery and recycling. The synthesis of atrazine was optimised in terms of addition sequence and rates of amine reagents and base (HCl acceptor), both by means of benchscale reactions and reaction calorimetry. Reaction energy profiles indicated that both the reaction of secondary amine/NaOH and primary amine/NaOH were virtually instantaneous. This implies that the reaction can be performed under feed control conditions. Of particular importance in ensuring high yields of high purity product was accurate temperature control (since both reaction steps are highly exothermic) and mixing. The latter was important in view of the rapid reaction of amine/NaOH with cyanuric chloride, as well as the possible reaction of mono-i, the first reaction intermediate, with IPA in cases of local excesses of reagent. Under optimum conditions, a yield of atrazine > 97% could be achieved where the resultant product was well within stipulated product specifications. In view of the results obtained, the following recommendations regarding the synthesis of atrazine in toluene as reaction solvent can be made: · Use a reagent addition sequence that staggers the addition of amine and NaOH in such a manner that amine is added first for a short while, followed by the simultaneous addition of amine and NaOH, and ending with NaOH. Use two reaction vessels in series, one for the IPA addition reaction and one for the MEA addition reaction. In this manner the reaction can be run on a continuous basis since no lag time between amine additions is required. Also, smaller reactors may be used whilst maintaining high production rates. Smaller reactors will improve both temperature control and mixing of reagents.
- Full Text:
- Date Issued: 2002
Exploring the perceived value of work as part of psychosocial rehabilitation of the state patient : Komani Hospital, Queenstown
- Authors: Crocker, Ann Petro
- Date: 2002
- Subjects: Work -- Psychological aspects Mentally ill -- Attitudes
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:5953 , http://hdl.handle.net/10962/d1007464
- Description: During the research an attempt was made to gain an understanding of the perceived value of work in psychosocial rehabilitation with the Sate patient at Komani Hospital. The respondents' motivation to work and what they gain from working, was investigated, as well as the experience of the nonworking respondents and their motivation not to work. To achieve this, ten respondents who were working and ten respondents who were not working, were interviewed. This study involves only a limited number of State patients at Komani Hospital and therefore findings cannot be generalised and also because the study was done at one Hospital only. A literature study was undertaken during which it was evident that work as part of vocational rehabilitation contributed to the well being of the mentally disabled person. It was also stated in the literature that the disabled person must be actively involved in his/her own rehabilitation planning and that the person must make conscious decisions to move away from the "sick" role and participate in his/her rehabilitation process. Interview schedules were developed. Response received from the twenty participants was analysed. The overall findings of the study showed that the majority of respondents who were working, were motivated by money. The fact that the respondents work from Hospital and therefore disrupt the Hospital routine, work with abled co-workers and feeling needed by the factory where they are employed. also emphasised the respondents' motivation to keep on working. The findings of the study with the non-working group showed that some respondents want to work, but there are not enough work opportunities available in and from Hospital. The non-working respondents are not interested in working at the occupational therapy department because the pay patients get for work done at the department is too little, and therefore they reject the work there. Some respondents do not want to work. whether work is available or not. The non-working group is largely dependent on staff and co-patients for an income, or tobacco. The predominant activity of the non-working group of respondents during the day, as well as that of the majority of the working group respondents during weekends was sleeping, talking to friends, and smoking. The research findings, conclusions and recommendations could contribute to a better understanding of patients and the value of work for the patient in a Psychiatric Hospital.
- Full Text:
- Date Issued: 2002
- Authors: Crocker, Ann Petro
- Date: 2002
- Subjects: Work -- Psychological aspects Mentally ill -- Attitudes
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:5953 , http://hdl.handle.net/10962/d1007464
- Description: During the research an attempt was made to gain an understanding of the perceived value of work in psychosocial rehabilitation with the Sate patient at Komani Hospital. The respondents' motivation to work and what they gain from working, was investigated, as well as the experience of the nonworking respondents and their motivation not to work. To achieve this, ten respondents who were working and ten respondents who were not working, were interviewed. This study involves only a limited number of State patients at Komani Hospital and therefore findings cannot be generalised and also because the study was done at one Hospital only. A literature study was undertaken during which it was evident that work as part of vocational rehabilitation contributed to the well being of the mentally disabled person. It was also stated in the literature that the disabled person must be actively involved in his/her own rehabilitation planning and that the person must make conscious decisions to move away from the "sick" role and participate in his/her rehabilitation process. Interview schedules were developed. Response received from the twenty participants was analysed. The overall findings of the study showed that the majority of respondents who were working, were motivated by money. The fact that the respondents work from Hospital and therefore disrupt the Hospital routine, work with abled co-workers and feeling needed by the factory where they are employed. also emphasised the respondents' motivation to keep on working. The findings of the study with the non-working group showed that some respondents want to work, but there are not enough work opportunities available in and from Hospital. The non-working respondents are not interested in working at the occupational therapy department because the pay patients get for work done at the department is too little, and therefore they reject the work there. Some respondents do not want to work. whether work is available or not. The non-working group is largely dependent on staff and co-patients for an income, or tobacco. The predominant activity of the non-working group of respondents during the day, as well as that of the majority of the working group respondents during weekends was sleeping, talking to friends, and smoking. The research findings, conclusions and recommendations could contribute to a better understanding of patients and the value of work for the patient in a Psychiatric Hospital.
- Full Text:
- Date Issued: 2002
Exploring the suitability of the evaluation criteria used in the MPT projects, by looking at hard and soft components of development programmes
- Authors: Ncapai, Wandile
- Date: 2002
- Subjects: Community development -- South Africa -- Eastern Cape , Community development , Economic development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3397 , http://hdl.handle.net/10962/d1018255
- Description: The study explores the suitability of the evaluation criteria used in Microprojects Programme Trust (MPT), by looking at hard and soft components of the development programme. In this sense hard components of development refer to those components of projects that are tangible and can be physically observed and can bring material changes to the life of the community. Soft components of development refer to those components of projects that bring qualitative transformation to the life of the community, i.e. increased levels of awareness, human well-being and the empowerment process that addresses the community's abstract needs, these are not tangible and often cannot be physically observed. Midway through its contract periods MPT evaluate all projects. The purpose of these mid term evaluations is to make recommendations to MPT on future approaches and methodology for community development and operations. The mid-term evaluation also influences the distribution and allocation of resources and funding. It was therefore vital that the criteria used are subject to tests and critical analysis so as to assess their validity. The assessment of the mid-term evaluation criteria used in MPT projects has been to further determine the appropriateness or suitability of the evaluation criteria as an instrument to measure and guide the MPT community development approach in the Eastern Cape. The method used was to conduct focus group discussions so as to get an insight into the local community situation as well as to assess non-tangible improvements and changes that have occurred in the life of the community as a result of the project. The information generated was used to compare what the community believe they achieved with what the official mid-term evaluation reports indicate was assessed and achieved and that was contrasted with what the literature recommends should have been assessed. The study found that the mid-term evaluations conducted on MPT projects have no social context in which the evaluations themselves were conducted. The terms of reference and criteria were based on the programme design which was formulated and compiled by the European Union without the participation of the local South African community. The findings also indicated that projects become unsuccessful or partly successful if the "soft" components which have a bearing on social and economic realities are neglected. The thesis ends with recommendations on how the mid-term evaluations as well as MPT programme can be developed to be more responsive to the needs as identified by the communities themselves. It is strongly believed that this study will provide a valuable contribution towards increasing the ability of MPT programme to bring about both material and qualitative transformation to the I ives of the disadvantaged community of the Eastern Cape whilst ensuring that the mid-term evaluations are developed and shaped to become an appropriate instrument to measure and guide MPT programme approach to community development.
- Full Text:
- Date Issued: 2002
- Authors: Ncapai, Wandile
- Date: 2002
- Subjects: Community development -- South Africa -- Eastern Cape , Community development , Economic development -- South Africa -- Eastern Cape , Economic development projects -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3397 , http://hdl.handle.net/10962/d1018255
- Description: The study explores the suitability of the evaluation criteria used in Microprojects Programme Trust (MPT), by looking at hard and soft components of the development programme. In this sense hard components of development refer to those components of projects that are tangible and can be physically observed and can bring material changes to the life of the community. Soft components of development refer to those components of projects that bring qualitative transformation to the life of the community, i.e. increased levels of awareness, human well-being and the empowerment process that addresses the community's abstract needs, these are not tangible and often cannot be physically observed. Midway through its contract periods MPT evaluate all projects. The purpose of these mid term evaluations is to make recommendations to MPT on future approaches and methodology for community development and operations. The mid-term evaluation also influences the distribution and allocation of resources and funding. It was therefore vital that the criteria used are subject to tests and critical analysis so as to assess their validity. The assessment of the mid-term evaluation criteria used in MPT projects has been to further determine the appropriateness or suitability of the evaluation criteria as an instrument to measure and guide the MPT community development approach in the Eastern Cape. The method used was to conduct focus group discussions so as to get an insight into the local community situation as well as to assess non-tangible improvements and changes that have occurred in the life of the community as a result of the project. The information generated was used to compare what the community believe they achieved with what the official mid-term evaluation reports indicate was assessed and achieved and that was contrasted with what the literature recommends should have been assessed. The study found that the mid-term evaluations conducted on MPT projects have no social context in which the evaluations themselves were conducted. The terms of reference and criteria were based on the programme design which was formulated and compiled by the European Union without the participation of the local South African community. The findings also indicated that projects become unsuccessful or partly successful if the "soft" components which have a bearing on social and economic realities are neglected. The thesis ends with recommendations on how the mid-term evaluations as well as MPT programme can be developed to be more responsive to the needs as identified by the communities themselves. It is strongly believed that this study will provide a valuable contribution towards increasing the ability of MPT programme to bring about both material and qualitative transformation to the I ives of the disadvantaged community of the Eastern Cape whilst ensuring that the mid-term evaluations are developed and shaped to become an appropriate instrument to measure and guide MPT programme approach to community development.
- Full Text:
- Date Issued: 2002
Extending the matching facilities of Linda
- Wells, George C, Chalmer, A B, Clayton, Peter G
- Authors: Wells, George C , Chalmer, A B , Clayton, Peter G
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430452 , vital:72692 , https://doi.org/10.1007/3-540-46000-4_34
- Description: This paper discusses the associative matching mechanism used in the Linda coordination language for the retrieval of data. There are a number of problems with this mechanism which are discussed in the light of the requirements of applications using Linda. A number of solutions to these problems have been proposed. These are discussed and compared with a new approach to solving these problems. The benefits and the limitations of the new approach are considered, showing how it provides a considerable improvement in this area.
- Full Text:
- Date Issued: 2002
- Authors: Wells, George C , Chalmer, A B , Clayton, Peter G
- Date: 2002
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430452 , vital:72692 , https://doi.org/10.1007/3-540-46000-4_34
- Description: This paper discusses the associative matching mechanism used in the Linda coordination language for the retrieval of data. There are a number of problems with this mechanism which are discussed in the light of the requirements of applications using Linda. A number of solutions to these problems have been proposed. These are discussed and compared with a new approach to solving these problems. The benefits and the limitations of the new approach are considered, showing how it provides a considerable improvement in this area.
- Full Text:
- Date Issued: 2002
Extension theorems on L-topological spaces and L-fuzzy vector spaces
- Authors: Pinchuck, Andrew
- Date: 2002
- Subjects: Topology , Vector spaces , Generalized spaces
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5405 , http://hdl.handle.net/10962/d1005219 , Topology , Vector spaces , Generalized spaces
- Description: A non-trivial example of an L-topological space, the fuzzy real line is examined. Various L-topological properties and their relationships are developed. Extension theorems on the L-fuzzy real line as well as extension theorems on more general L-topological spaces follow. Finally, a theory of L-fuzzy vector spaces leads up to a fuzzy version of the Hahn-Banach theorem.
- Full Text:
- Date Issued: 2002
- Authors: Pinchuck, Andrew
- Date: 2002
- Subjects: Topology , Vector spaces , Generalized spaces
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5405 , http://hdl.handle.net/10962/d1005219 , Topology , Vector spaces , Generalized spaces
- Description: A non-trivial example of an L-topological space, the fuzzy real line is examined. Various L-topological properties and their relationships are developed. Extension theorems on the L-fuzzy real line as well as extension theorems on more general L-topological spaces follow. Finally, a theory of L-fuzzy vector spaces leads up to a fuzzy version of the Hahn-Banach theorem.
- Full Text:
- Date Issued: 2002
Finite element simulations of shear aggregation as a mechanism to form platinum group elements (PGEs) in dyke-like ore bodies
- Authors: Mbandezi, Mxolisi Louis
- Date: 2002
- Subjects: Platinum group , Magmas , Shear flow , Geophysics , Terrestrial heat flow
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5561 , http://hdl.handle.net/10962/d1018249
- Description: This research describes a two-dimensional modelling effort of heat and mass transport in simplified intrusive models of sills and their feeder dykes. These simplified models resembled a complex intrusive system such as the Great Dyke of Zimbabwe. This study investigated the impact of variable geometry to transport processes in two ways. First the time evolution of heat and mass transport during cooling was investigated. Then emphasis was placed on the application of convective scavenging as a mechanism that leads to the formation of minerals of economic interest, in particular the Platinum Group Elements (PGEs). The Navier-Stokes equations employed generated regions of high shear within the magma where we expected enhanced collisions between the immiscible sulphide liquid particles and PGEs. These collisions scavenge PGEs from the primary melt, aggregate and concentrate it to form PGEs enrichment in zero shear zones. The PGEs scavenge; concentrate and 'glue' in zero shear zones in the early history of convection because of viscosity and dispersive pressure (Bagnold effect). The effect of increasing the geometry size enhances scavenging, creates bigger zero shear zones with dilute concentrate of PGEs but you get high shear near the roots of the dyke/sill where the concentration will not be dilute. The time evolution calculations show that increasing the size of the magma chamber results in stronger initial convection currents for large magma models than for small ones. However, convection takes, approximately the same time to cease for both models. The research concludes that the time evolution for convective heat transfer is dependent on the viscosity rather than on geometry size. However, conductive heat transfer to the e-folding temperature was almost six times as long for the large model (M4) than the small one (M2). Variable viscosity as a physical property was applied to models 2 and 4 only. Video animations that simulate the cooling process for these models are enclosed in a CD at the back of this thesis. These simulations provide information with regard to the emplacement history and distribution of PGEs ore bodies. This will assist the reserve estimation and the location of economic minerals.
- Full Text:
- Date Issued: 2002
- Authors: Mbandezi, Mxolisi Louis
- Date: 2002
- Subjects: Platinum group , Magmas , Shear flow , Geophysics , Terrestrial heat flow
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5561 , http://hdl.handle.net/10962/d1018249
- Description: This research describes a two-dimensional modelling effort of heat and mass transport in simplified intrusive models of sills and their feeder dykes. These simplified models resembled a complex intrusive system such as the Great Dyke of Zimbabwe. This study investigated the impact of variable geometry to transport processes in two ways. First the time evolution of heat and mass transport during cooling was investigated. Then emphasis was placed on the application of convective scavenging as a mechanism that leads to the formation of minerals of economic interest, in particular the Platinum Group Elements (PGEs). The Navier-Stokes equations employed generated regions of high shear within the magma where we expected enhanced collisions between the immiscible sulphide liquid particles and PGEs. These collisions scavenge PGEs from the primary melt, aggregate and concentrate it to form PGEs enrichment in zero shear zones. The PGEs scavenge; concentrate and 'glue' in zero shear zones in the early history of convection because of viscosity and dispersive pressure (Bagnold effect). The effect of increasing the geometry size enhances scavenging, creates bigger zero shear zones with dilute concentrate of PGEs but you get high shear near the roots of the dyke/sill where the concentration will not be dilute. The time evolution calculations show that increasing the size of the magma chamber results in stronger initial convection currents for large magma models than for small ones. However, convection takes, approximately the same time to cease for both models. The research concludes that the time evolution for convective heat transfer is dependent on the viscosity rather than on geometry size. However, conductive heat transfer to the e-folding temperature was almost six times as long for the large model (M4) than the small one (M2). Variable viscosity as a physical property was applied to models 2 and 4 only. Video animations that simulate the cooling process for these models are enclosed in a CD at the back of this thesis. These simulations provide information with regard to the emplacement history and distribution of PGEs ore bodies. This will assist the reserve estimation and the location of economic minerals.
- Full Text:
- Date Issued: 2002